Hydro-pneumatic press



July 4, 1961 C. H. M CREA HYDRO-PNEUMATIC PRESS Filed Dec. 23, 1959 Fig.2. 70 ea l E A w: Z

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INVENTOR Charles H. McCrea BY ZWIW new and unique press which iscontrolled directly bylinput of pneumatic pressure and which is actuatedby hydraulic forces in such a way as to have a first stage of operationhaving an inherently low force to movement ratioand a second phase ofoperation which has a high force to movement ratio due to the action ofan integral intensifier. v

Anotherobject of this invention is to provide a novel press having ahousing and a press ram which is reciprocally mounted within thehousing. The bottom portion of the ram opens to the housing and the topportion. of

the housing forms a fluid seal where the housing and the ram areslidablyengaged. The spacing within the hous- United States Patent Q ing betweenthe housing and the ram walls and a portion 1 of the interior of the ramare filled with a hydraulic fluid. A pneumatically actuated piston ismounted 'withinthe ram on an air cushion over the hydraulic fluid to.force the hydraulic fluid down through the bottom of thev ram and intothe housing. The force thus generated is translated into physicalmovement of the ram upwardly to form a press function.

As a further object of the invention the bottom of: the piston is formedwith a stem formed to mate a restricted aperture on the bottom of theram. When the piston is moved down to the point where the stem engagesthe aperture fluid communication between the ram andoil: reservoir isblocked to cause a hydraulic intensifying action for the generation ofextremely high hydraulic pressures.

A feature and advantage of this invention is that the press requiresonly three basic parts which are relatively movable to each other, ahousing, a ram and a piston.

An other feature and advantage of this invention is that the intensifiercomprises only the integral structure of the piston and the ram in sucha way as to completely eliminate the need of external hydraulic valvingand other intensifying arrangements previously employed to create fluidintensifiers. An other important object of this invention is theprovision of a buffer air chamber between the piston and the hydraulicfluid which can be adjusted as to pressure to provide means foradjusting the home or lower position of the ram.

A still further object of this invention is to provide a press in whicha stemmed piston mounted within the ram itself'establishes both thefunction of main ram movement and an intensifying action.

A further feature and advantage of this invention is that the press maywork in an upright vertical, inverted vertical or horizontal position. 7

Other objects of the present invention will become apparent upon readingthe following specification,- and referring'to the accompanying drawingsin which similar characters of reference represent corresponding partsin each of the several views.

In the drawings:

FIG. 1 is -a schematic side elevational view of the invention showingthe ram in the home or lowermost position.

FIG. 2 is a view similar to FIG. 1 but showing the ram in anintermediate position with the piston in a position to create theintensifying action.

FIG. 3 is a view similar to FIGS. 1 and 2 showing the ram in its mostextended position.

2,990,687 Fatented July 4, 1961 .FIG. 4 is an enlarged cross-sectionalview showing the needle opening for allowing air to pass into the ram.The principal embodiment of the press comprises a main frame A, a pressram B reciprocally mounted for movement within the housing or frame Aand a piston C mounted within ram B for slidable movement therein.

Press ram B is arranged to move upwardly relative to the housing byvirtue of the downward movement of piston C within the ram. This actionis facilitated by pneumatic pressure which causes the piston to movedown to cause transference of oil from the bottom portion of the raminto the oil reservoir area 15 between the ram and the housing.

Ram B is formed with a round outer cylindrical wall 18- and with aninner cylindrical wall surface 19.

Piston C is slidably mounted within cylindrical wall 19 and is providedwith an O-ring 21 so that a good fluid tight seal exists. The pistondivides the inner part of the ram into a compression chamber 25 betweenthe top 26 of the piston and the top 28 of the ram and an air bufferchamber 30 formed under the piston between the bottom face 31 of thepiston and the top 34 of the oil within the ram.

A stem 38 depends downwardly from the bottom 31 of piston C to a pointbelow top surface 34 of the oil level in the ram.

A floating'spacer disk 39 is mounted on top surface 34 of oil reservoir15 to prevent fluid communication between the air and buffer chamber inoil reservoir 15. Disk 39 is slidably mounted relative to both ram wall19 and stem 38.

The bottom of ram B is provided with a bottom plate 41 having arestricted aperture 42 which is formed in cross-sectional dimensionsubstantially equal to the crosssectional dimension of stem 38.

An O-ring 44 is provided within aperture 42 to provide a fluid tightseal between stem 38 and the aperture when the stem engages the apertureas will hereinafter be explained.

The top portion of housing A is provided with an annular inner top face45 which is provided on its inner edge 46 with O-rings to form a guideand fluid tight seal between top face 45 and outer wall .18 of press ramB.

A port 55 is provided in the side wall of housing A which is providedwith fittings 56 and a hose 57 so that hydraulic fluid or oil may beinserted within oil reservoir 15. The side wall of piston C is providedwith an ex tremely restricted aperture on its inside face indicated at58 which is connected to a fitting 59 and a hose 60 to allow air to befed into air buffer chamber 30.

A pump 61 and a regulator 62 are provided in the circuit connected tohose 60 to provide means for establishing substantially equal pressureat all times within the buffer chamber.

The control of the press is eflected by injecting air in or bleeding airout of compression chamber 25. This is done through a port 68 which isfed through a fitting 69 and a hose 70. Hose 70 is connected to a valve'71 which in turn is fed by a pump 73. Valve 71 is a three-way valveallowing either air to pass into compression chamber 25 or to bleed airfrom the compression chamber; The end of stem 38 is tapered at to alloweasier en'- gagement with aperture 42.

In operation hydraulic fluid is placed within oil reservoir 15 so thatthe entire area between ram B and housing A is filled with oil and sothat the oil reaches a level approximately half way between the upperand lower ends of ram B. It is important that the usual precautions beemployed to completely bleed off any air that might be'in the oil orhydraulic fluid.

Air is then forced into air buffer chamber 30. The

- air pressure in chamber 30 will determine the home or Ln. Ln...

lower position of the ram. This is due to the fact that greaterintensity of air pressure within bufier chamber 30 causes the ram toseat at a higher position relative to the reservoir. Consequently thestarting position for the ram can be adjusted by adjusting regulator 62to maintain the pressure at a predetermined level. Lower bufier airpressure will cause the ram to return to its lowest possible positionand a higher pressure will allow the mm to return to selectedintermediate positions after each operation.

Once the pressure has been regulated within buffer chamber 30 valve 71is actuated to cause air to enter compression chamber 25. The pressureof air within compression chamber 25 causes piston C to move downwardlyto cause the air bulfer chamber 30 to force the oil within the ram downand out through aperture 42 intooil reservoir 15. The transfer of oilfrom the ram housing into main chamber A forces ram B to move upwardly.The

force generated is directly proportional to the pressure withincompression chamber 25 until stem 38 engages aperture 42 as seen inFIGS. '2 and 3. Under these conditions there can be no transfer of oilfrom the ram to the housing. Therefore the only further oil displacementwhich is caused by further lowering of piston C is that of the stemprotruding into the lower reservoir. This creates a tremendousintensifying action and relatively small ram movement.

To drop the press, valve 71 is simply moved to a bleeding positionwherein the inherent weight of the ram will cause the ram to drop to apoint equilibrium. This point is established by maintaining pressurewithin buffer area 30 at the determined pressure.

Floating spacer disk 39 need not be utilized if the press is to beoperated in a vertical upright position. However, with the provision ofdisk 39 the press can be operated upside down or horizontally in thatthere can be no transference or fluid communication past the disk.

Aperture 58 for supplying air to the butter chamber is of pinhole sizeso that O-ring 21 on piston C will be able to pass the aperture withoutcausing undue wear on the O-ring 21 or the cylindrical wall. It is alsoto be noted that the aperture 58 is located on the upper portion of theram so that as the piston is lowered the butter chamber is completelysealed and it is only after the piston raises to its upward homeposition that the bufller chamber is in fluid communication to beequalized by air pressure from regulator 62.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, it is understood that certain changes and modificationsmay be practiced within the spirit of the invention as limited only bythe scope of the appended claims.

What is claimed:

1. A press for obtaining large ratios of displacement to force in afirst stage and low ratios in a successive stage comprising, incombination, a housing having a bearing aperture formed through onesurface, a hollow bore ram slidably supported in the bearing aperturefor movement between extended and retracted positions and cooperatingwith the housing to form a fluid tight chamberbetween the housing andthe ram, said ram having a fluid communicating aperture formed throughits interior end and forming a fluid communicating passageway thatextends between the interior of said housing and the interior of saidram, hydraulic fluid in said chamber and in a portion of the interior ofsaid ram, a piston with a rod aifixed thereto slidably supported in thebore of said ram, said rod being of a selected length to be spaced fromthe fluid communicating aperture during the first stage and to enter thefluid communicating aperture to prevent the passage of fluid through theaperture during the successive stage, a gas cushion intermittent the rodside of the piston and the hydraulic fluid in the interior of said ram,and

means to move the ram from a retracted position to an extended positionthrough the first and successive stages by the movement of the pistontoward the interior end of said ram.

2. A press comprising a housing containing hydraulic fluid, a hollow ramslidably mounted with a fluid tight seal in said housing for movementbetween extended and retracted positions relative to said housing, saidram having an aperture formed in its lower end affording a fluidcommunication passageway between the interior of the ram and theinterior of the housing to allow hydraulic fluid in the housing to passinto the interior of said ram, a piston slidably mounted within theinterior of the ram,

sa compressible gas cushion formed between said piston 'and the surfaceof the fluid extending into the interior of said ram, means forsupplying preselected quantities of gas to the space between the pistonand the outer end of the ram to displace the piston toward said lowerend, and a stem depending from said piston toward the apertured end ofthe ram having a cross-sectional dimension substantially equal to thecross-sectional dimension of the fluid communicating aperture andaxially aligned therewith, said stem being formed of a length sufficientto engage the surfaces defining the aperture to block the passage offluid between the interior of the ram and the exterior of the housing aslong as the piston is less than a predetermined distance from the innerend of said ram.

3. 'A press for obtaining large ratios of displacement to force in afirst stage and low ratios in a successive stage comprising, incombination, a housing having a bearing aperture formed in one surface,a hollow ram slidably supported in the bearing aperture for movementbetween extended and retracted positions and to form a liquid tight sealbetween the housing and the ram, said ram having an aperture formed inthe inner end that opens into said housing, a suflicient quantity ofhydraulic liquid in the interior of the housing and in the interior ofsaid ram to maintain the interior of said housing completely filled withliquid and a liquid column in a portion of the interior of said ram atall times, a piston and rod combination slidably supported in theinterior of the ram 'so that the rod enters the aperture formed in theinner end of said ram at a preselected point in its travel toward saidinner end to close the communicating passage between the interior ofsaid ram and said chamber, means for establishing a preselected gascushion intermediate the rod side of the piston and the hydraulic fluidcolumn in the interior of said ram, and means including a variablepneumatic source to displace the piston toward the inner end of said ramto move the ram toward its extended position whereby during the firststage, with the passage between the interior of the housing and the raminterior open, the ram is moved partially towards its extended positionby transferring fluid from the interior of the ram to the interior ofthe housing and during the second stage, with the passage between theinterior of the ram and the chamber blocked by the entrance of the rodinto the aperture formed in the inner end of said ram, the ram is movedto its fully extended position by projecting said rod into the interiorof said housing.

4. A press according to claim 3 and wherein a disk is slidably supportedbetween the gas cushion and the column of hydraulic fluid in theinterior of the ram formed to provide a gas tight seal therebetween.

5. A press according to claim 4 having gas injection means to injectgas. into the gas cushion between the hydraulic fluid in the interior ofthe ram and said piston.

6. A press comprising a housing containing hydraulic fluid, a hollow ramslidably mounted in a fluid tight seal for movement into and out of saidhousing, an aperture on the bottom portion of said ram and incommunication ram, a body of gas between said piston and the aperture,means for adjustably controlling gas pressure against said piston in thebore of said ram in the area between said piston and the top portion ofsaid ram to force said ll piston to move toward said aperture, and astem depending from said piston having a cross-sectional dimensionsubstantially equal to the cross-sectional dimension of said apertureand axially aligned therewith, said stem being formed of a lengthsuflicient to mate with said aperture to close fluid communicationbetween the bore of the ram and the interior of the housing when saidpiston is less than a predetermined distance from the apertured end ofsaid ram.

References Cited in the file of this patent UNITED STATES PATENTS

